The internal combustion engine powered by fossil fuel (gasoline or diesel) is the dominant form of propulsion for motor vehicles, this despite the fact that significant efforts have been made to develop both an alternative fuel source and engines which will run on these fuels for an extended period of time. Alternative power sources have a long history of development. Many factors have motivated this development. One of the earliest reasons for developing alternative fuels and engine systems has been based on efforts to remove reliance on traditional fuel sources. More recently attention has been focused on the reduction of greenhouse gases which are known to contribute to global warming. These driving forces have increased the pace of the development efforts and research studies related to alternative fuel systems.
Some examples of alternative fuels include natural gas, hydrogen and bio-fuels such as ethanol. As a fuel ethanol has proven very attractive. Today ethanol blend fuels and he engines capable of running on ethanol blends range from E0 (today's typical gasoline having no ethanol content) to E85 (having 85% ethanol content with 15% gasoline content). Ethanol can be produced readily from certain grain crops, particularly corn. The use of ethanol also reduces the production of greenhouse gases since it is a renewable source of fuel with a CO2 neutral cycle. Ethanol has a high potential to become economically more beneficial over today's widely available fuels.
As a fuel, ethanol has long shown a significant potential as a substitute for conventional gasoline. Today's fuel standards (e.g., ASTM D4814) allow up to 10% ethanol content for regular gasoline and also in the use of E85. Accordingly, flexible fuel vehicles (FFV), which can run on fuels up to E85 ethanol content, are already in several markets around the world. However, because of the lack of fuel infrastructure and the consequential failure of fuel availability, flexible fuel vehicles failed to take advantage of fuel flexibility. One of the obstacles to wider acceptance by the end user has been the reduction in usable vehicle range (reduced heating value) and the lack of tax reductions on the price of bio-fuels at the fuel service center. For example, while flexible fuel vehicles experience no loss of performance when operating on E85, a gallon of ethanol contains less energy than a gallon of gasoline, resulting in the flexible fuel vehicle typically getting about 20-30% fewer miles per gallon when fueled with bio-fuels such as E85. Part of this inefficiency is due to the lack of base engine optimization that is seen in current flexible fuel vehicles. Particularly, no advantage has been taken of beneficial bio-fuel fluid properties such as increased octane numbers.
Some of the high ethanol content fuel usage penalties can be eliminated or reduced by developing dedicated control algorithms and hardware to take advantage of certain thermodynamic properties of ethanol. With the recent market introductions of more sophisticated subsystems, for example, direct fuel injection, variable valve timing and turbo-charging, the complexity of engine control systems has significantly increased. So-called downsized systems can provide high power density under full load and maintain very good part load fuel economy due to lower friction and reduced losses because of their smaller displacement. Today's systems are capable of accurately controlling such modern gasoline engines. It is believed that these advancements can also be used to further boost performance of flexible fuel vehicle systems by the development of intelligent control algorithms along with modifications to engine hardware.
Accordingly, as with so man areas of technology, there is room for improvement in the use of bio-fuels in flexible fuel vehicles.